12 Signal processing
RF amplification
The signal that is read from the compact disc and contains the data information is the RF signal, that consists of the sum of signals (A + B + C + D) from the main spot detector. At this stage, the signal is a weak current signal and requires current-to-voltage conversion, amplification and waveform shaping. The CDP-101 RF amplifier circuit is shown in Figure 12.1. IC402 is a current-to-voltage converter and amplifier stage, while IC403 is an offset amplifier, correcting the offset voltage of the RF signal and delivering the amplified RF signal.
Figure 12.2 shows the waveshaper circuit used in the CDP-101. Because the RF signal from the RF amplifier is a heterogeneous signal due to disc irregularities, the ...
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